Annual report pursuant to Section 13 and 15(d)

Activity in Deferred Compensation Program (Detail)

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Activity in Deferred Compensation Program (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Stockholders Equity Note [Line Items]      
Balance at end of period $ 7,035 $ 7,979  
Balance at end of year (2) (2)  
Treasury Stock
      
Stockholders Equity Note [Line Items]      
Balance at beginning of period (103) (108) (121)
Reinvested dividends (4) (4) (3)
Options exercise deferrals   (1)  
Benefit payments 19 10 16
Balance at end of period (88) (103) (108)
Balance at beginning of year (2) (2) (2)
Reinvested dividends         
Options exercise deferrals         
Benefit payments         
Balance at end of year (2) (2) (2)
Deferred Compensation Obligations
      
Stockholders Equity Note [Line Items]      
Balance at beginning of period 103 108 121
Reinvested dividends 4 4 3
Options exercise deferrals   1  
Benefit payments (19) (10) (16)
Balance at end of period $ 88 $ 103 $ 108